1. Field of the Invention
The present invention relates to stoves or heaters, including wood-burning stoves, and more particularly to a device for preventing flames, smoke or other products of combustion from blowing back through the fuel loading door when that door is opened.
2. Description of the Prior Art
Stoves or heaters of the type burning solid fuels such as wood or coal and employing a combustion chamber housing which is enclosed by an outer housing are known in the prior art. The combustion chambers of such stoves have normally included a fuel loading door through which fuel is introduced into the combustion chamber with another door being provided in the outer housing to permit access to the fuel loading door. Stoves and heaters of the foregoing type frequently also include a combustion air inlet having control means for varying the amount of air permitted to enter the combustion chamber. A damper is provided to regulate the inflow of combustion air through the combustion air inlet with the combustion air frequently being largely cut off when the damper is closed; however, the solid fuel and the gases emitted therefrom remain in the combustion chamber and are readily ignitable upon receiving a fresh supply of oxygen. Under these conditions, the opening of the fuel loading door of the combustion chamber results in the rapid admission of air into the combustion chamber causing the gases and solid fuel in the combustion chamber to be immediately ignited and frequently causing flames, smoke and other products of combustion to rapidly blow back through the open fuel loading door.
The prior art discloses devices intended for use in connection with such stoves for preventing flames, smoke and other products of combustion from blowing back through the fuel loading door whenever that door is opened under the above-described conditions. Thus, for example, U.S. Pat. No. 4,030,479, entitled "Solid Fuel Heater With Blowback Prevention Means," issued June 21, 1977, to Webb, discloses an elongated cam member for opening a valving means comprising a pivotable closure member which is used to regulate the flow of air into the combustion chamber. One end of the elongated cam member is pivotably connected to the outer housing door and the other end is operably connected to the closure member. Opening the outer housing door moves the elongated cam member thereby opening the pivotable closure member to admit combustion air so that the subsequent opening of the fuel feed door to the combustion chamber will not result in a rapid inflow of air and the ignition of the products in the combustion chamber to create a "dangerous blowback problem". U.S. Pat. No. 2,352,057, entitled "Safety By-Pass for Stoves and Furnaces," issued June 20, 1944, to Wingert, provides a means for automatically releasing the gases accumulated over a fuel bed into a smoke stack when the fuel feed door is opened. U.S. Pat. No. 713,066, entitled "Damper Mechanism", issued Nov. 11, 1902, to Cooper, discloses a means for opening a damper automatically with the opening of the feed door to the combustion chamber; the Cooper patent does not disclose a means for increasing the air supply to the combustion chamber prior to the opening of the fuel feed door. Other means for moving a damper for the admission of air as the fuel feed door is opened by means of interconnecting linkage are disclosed in U.S. Pat. No. 472,728, entitled "Furnace", issued Apr. 12, 1892, to Decker, et al., and in U.S. Pat. No. 204,406, entitled "Stove Damper", issued May 28, 1978, to White.
All of these prior art devices require interconnecting linkage to actuate a valve or damper, and all of these prior art devices except the Webb device are actuated by the opening of the fuel feed door to the combustion chamber rather than by the outer housing door so that the air supply to the combustion chamber is increased simultaneously with the opening of the fuel feed door rather than prior to the opening of the fuel feed door. The present invention is an improvement over these prior art devices because it increases the air supply to the combustion chamber before the fuel feed door is opened without requiring interconnecting linkage.